1. Field of the Invention
This invention pertains to differential systems for motor vehicles and, more particularly, the invention pertains to a method for controlling an axle shaft endplay in a differential assembly.
2. Description of the Prior Art
In conventional drivelines, particularly those for rear wheel drive vehicles, the left-hand and right-hand axle shafts extend laterally from a differential assembly that includes side bevel gears in continuous meshing engagement with differential pinion mate gears supported rotatably on a pinion shaft carried on a differential case. The differential case is driven rotatably by a set of meshing bevel gears, one of which is driven by a drive shaft disposed substantially perpendicular to the axle shafts. The side bevel gears typically are connected rotatably to the axle shafts by a spline connection formed on a shoulder near the inboard ends of the axle shafts. Each axle shaft includes also a terminal shoulder at its axially innermost extremity, the terminal shoulder located adjacent the differential pinion shaft.
Located between the shoulders on the axle shaft is an annular groove that is axially aligned with the recess formed on the corresponding side bevel gear. A slotted washer or retainer ring, fitted within the groove of the axle shaft and the recess in the side bevel gear, limits outward axial movement of the axle shaft relative to the side bevel gear. However, each axle shaft is free to move along the spline connection axially inward toward the differential pinion shaft. This amount of an internal axial clearance is called an axle shaft endplay.
The excessive amount of the endplay in the differential assemblies allows the axle shafts to shift axially inwardly relative to the differential case and jar or knock against the pinion shaft. Moreover, the conventional assembly can lead to grinding away of the end of the side yoke causing excessive negative camber, which in turn can lead to uneven tire wear and poor driving stability. It can also cause particles of the side yokes to embed themselves in the differential clutch plates causing slippage of the differential unit resulting in a clunking or thumping noise. If the wear is left unchecked, it may increase to a point where the flange will shear or cut into the differential case causing a leakage of fluid and ultimately leading to complete destruction of the differential assembly.
The current retention method of the axle shaft does not allow an endplay control. Therefore, the need exists to control the endplay of the axle shaft in order to provide a predetermined desired endplay in accordance with vehicle manufacturer""s specification and/or depending on the operational conditions of the axle assembly.
It is an object of the present invention to provide a device and method for controlling an axial displacement (or endplay) of an axle shaft in a differential assembly including an axle shaft having external splines adapted to mate with internal splines of a differential side gear and an annular groove located adjacent to a terminal shoulder provided at an inboard end of the axle shaft. The annular groove is provided for receiving a retainer ring limiting an axial displacement of said axle shaft in an outboard direction.
The device, according to the present invention, for controlling an axle shaft endplay in the differential assembly comprises a shim ring disposed on the inboard end of the axle shaft between the retainer ring and the side gear. The shim ring has a selective thickness such as to provide a desired axle shaft endplay.
The method, according to the present invention, for controlling an axle shaft endplay in a differential assembly is preformed in the following manner: first, a value of a desired endplay xcex4=xcex4P is determined based on particular operational conditions and the type of the differential assembly. A differential mechanism is partially assembled including side gears and bevel pinion gears in continuous meshing engagement with the side gears in a differential case. Then, a thickness WS of the shim ring is calculated that would provide the desired endplay xcex4P. In accordance with the present invention, the manufacturer of the axle assemblies is provided with an endplay controlling kit that includes a plurality of the shim rings of assorted thickness. The appropriate shim ring having the determined thickness WS calculated during the previous step of the present method, is selected from the plurality of the assorted shim rings of the endplay controlling kit. Next, the axle shaft is inserted into the differential case through the side gear, and the selected shim ring is mounted to the axle shaft. The retaining ring is then mounted in the annular groove, and the axle shaft is pulled outboard to sandwich the shim ring between the side gear and the retainer ring. Finally, remaining components of the differential assembly are assembled, thus, completing the process of assembling the differential assembly. The plurality of the shim rings in the endplay controlling kit have the thickness ranging from a thinnest having the thickness WSmin to the thickest having the thickness WSmax. The thinner shim rings provide more endplay, and the thicker shim rings provide less endplay. Also, the differential assembly with a zero axle endplay may be provided.
Therefore, the present method for controlling the endplay of the axle shaft solves the need for a solution to the problem of controlling the axle shaft endplay in the vehicular differential assemblies in a simple, efficient and inexpensive manner.
These and other benefits of the present invention will become apparent from the following description and associated drawings.